>>28534495 (OP)I dont know the different models that well, go watch that radar detector dude on YT and you'll learn a lot about what's important to you.
I got an R8 about 2 yrs ago and super happy with it, the arrows are a huge help to understand what's going on around you.
If anything I'd say the R8 Ka band performance is so amazingly good it's almost too good... you'll get warnings well over a mile away in average conditions. It's unbelievable.
The ability to gps tag and auto-mute/mark false signals on your normal route is great.
No ragrets on the purchase.